Change info to debug

[amab8901]

current:

producer.rs

info!(
    "Message with key {} delivered to partition {} at offset {}",
    message.key, partition, offset
);

requested:

producer.rs

debug!(
    "Message with key {} delivered to partition {} at offset {}",
    message.key, partition, offset
);

motivation:

it's spammy and the info isn't useful unless I'm debugging.

[amab8901]

I think an even better solution would be to remove the log altogether and instead put the status in the return value of the function so that the user can decide what to do with it.